Preliminary investigations have demonstrated that hypertonic mannitol improves the contractile function and total coronary blood flow of ischemic canine myocardium and the contractile performance of hypoxic cat papillary muscle. The studies outlined in this continuation request of a NIH-funded grant will attempt to further extend the earlier observations. Anesthetized and awake, intact dog preparations with acute and chronic myocardial ischemia and isolated cat papillary muscles will be utilized to study the ability of mannitol to alter regional myocardial blood flow, metabolism, performance, and cell size in ischemic canine myocardium and hypoxic cat papillary muscles. The influence of mannitol on organ function and histology will also be determined.